//
// Copyright (c) 2004-2024 Jaroslaw Kowalski <jaak@jkowalski.net>, Kim Christensen, Julian Verdurmen
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
//
// * Neither the name of Jaroslaw Kowalski nor the names of its
//   contributors may be used to endorse or promote products derived from this
//   software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
//

namespace NLog.Internal
{
    using System;

    /// <summary>
    /// FormatProvider that renders an exception-object as $"{ex.GetType()}: {ex.Message}"
    /// </summary>
    internal sealed class ExceptionMessageFormatProvider : IFormatProvider, ICustomFormatter
    {
        internal static readonly ExceptionMessageFormatProvider Instance = new ExceptionMessageFormatProvider();

        string ICustomFormatter.Format(string format, object arg, IFormatProvider formatProvider)
        {
            if (arg is Exception exception)
            {
                exception = GetPrimaryException(exception);
                return $"{exception.GetType().ToString()}: {exception.Message}";
            }
            else
            {
                return string.Format("{0}", arg);
            }
        }

        private static Exception GetPrimaryException(Exception exception)
        {
#if !NET35
            if (exception is AggregateException aggregateException)
            {
                if (aggregateException.InnerExceptions?.Count == 1)
                {
                    var innerException = aggregateException.InnerExceptions[0];
                    if (!(innerException is AggregateException))
                        return innerException;  // Skip calling Flatten()
                }

                aggregateException = aggregateException.Flatten();
                if (aggregateException.InnerExceptions?.Count == 1)
                {
                    return aggregateException.InnerExceptions[0];
                }
            }
#endif
            return exception;
        }

        object IFormatProvider.GetFormat(Type formatType)
        {
            return (formatType == typeof(ICustomFormatter)) ? this : null;
        }
    }
}
